A typical wireless network is comprised of multiple base stations. Alternatively referred to as cell sites or cells since their coverage area may resemble a cell, a base station may communicate with one or more mobile devices within their coverage area. Across the wireless network, one or more transmitters may communicate with one or more receivers across a common communications medium. With multiple access technologies, air interface channels are segmented so that they may be shared by multiple users. For example, a channel may be segmented into frequencies for FDMA technology, into codes for CDMA technology, into time slots for TDMA technology, etc. The segments of the air interface channels are referred to herein as resources.
There may be situations where all resources are used by all base stations in the wireless network. When this occurs, there may be significant interference between base stations which leads to unreliable or slower communication links. For instance, in emerging networks such as the heterogeneous networks being considered by 3GPP standards, there may be both macrocells (typical base stations that are intended to provide service over a wide geographic area) and small cells (base stations with smaller form factors and smaller service areas due to significantly reduced transmit powers and antenna gains) in the same vicinity. The principal objective of deploying small cells within the coverage area of macrocells is to provide additional system capacity (by offering additional resources), perhaps to users that are tightly clustered in certain spots and the available resources offered by the macrocell must be shared by many users. However, in heterogeneous networks where macrocells and small cells share the same resources, the significantly higher transmit powers and antenna gains of the macrocells lead to exceedingly small coverage areas for the small cells thus rendering throughput/capacity benefits to only a small number of users. Further, while a small number of users may communicate at higher rates (primarily because they share the available resources with fewer users), they may only demand low rate services (e.g., VoIP) or have large periods of data inactivity where the higher achievable rates cannot be exploited. In such a case, the expected gains would not be achieved.
In order to avoid interference between neighboring base stations, the communication resources available to the wireless network may be divided into disjoint subsets called partitions. It is typical to statically and exclusively allocate a set of resources to a distinct set of users in the network. In one example (e.g., a reuse ⅓ deployment of the 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE)), the frequency band available to the wireless network may be partitioned into three mutually exclusive sets (frequency sets 1, 2, and 3) which together constitute the entire frequency band of the wireless network. These three sets of frequencies may be allocated to three mutually exclusive sets of base stations (sets A, B, and C) which together represent all of the base stations in the wireless network. In this type of resource allocation, frequency set 1 is exclusively and statically assigned to base stations in set A, frequency set 2 is exclusively and statically assigned to base stations in set B, and frequency set 3 is exclusively and statically assigned to base stations in set C. The exclusive assignment precludes a base station in set A from using resources in set 2 or set 3.
Allocating different resources to small cells and macrocells would benefit heterogeneous deployments since small cell users would no longer experience strong interference from macrocells. As a result, the spectral efficiency and coverage area for small cells would improve. However, the exclusive partitioning of resources may lead to a sizeable loss in service rates.